1. Field of the Invention
This invention relates to a sound reproducer for a high definition television (hereinafter referred to as "Hi-vision") system and, more particularly, to a sound reproducer of the type for reproducing surrounding sounds in accordance with a Hi-vision sound system by making use of an Audio-Video (AV) amplifier originally arranged for the Dolby (registered trademark) surround system which is one of two-channel sound surround systems.
i. Description of the Prior Art
The Hi-vision system is a television system proposed for the next generation of television systems and is capable of reproducing powerful, fine-grained, rich with colors and high-definition images in a large-sized display as compared with the existing television systems. Accordingly, it is required to provide a sound reproducer of the Hi-vision system with a sense of presence and high quality fit for the high quality Hi-vision images.
To study a sound reproducing system suitable for the Hi-vision images, experiments for evaluating a number of stereophonic sound reproducing systems have been implemented in order to determine the optimum number audio channels to be employed and an arrangement of speakers. Through these experiments, it was found that a 3-1 sound reproducing system is the most suitable in all respects, for reproducing a surrounding sound effect for the Hi-vision images. The 3-1 sound reproducing system has an optimum number of three audio channels and an optimum arrangement of speakers such that three front speakers for the three audio channels and two rear speakers for a monaural audio channel. In the arrangement of the front and rear speakers, two speakers are arranged at the right (R) front and left (L) front of the listener and that one speaker at the center (C) front, while two speakers are arranged at the right (R) rear and left (L) rear of the listener.
The Hi-vision 3-1 sound system is a kind of four-channel stereophonic sound reproducing system consisting of three front audio channels and one rear audio channel and is capable of realizing a so-called surrounding sound effect fit for Hi-vision images as if the listener were in the midst of the reproduced sounds.
In order to reproduce audio signals in accordance with the Hi-vision 3-1 sound system by employing a two-channel stereophonic amplifier, it is necessary to adapt at least three amplifiers in total, one amplifier for the right and left front audio signals, one amplifier for the center front audio signal and one amplifier for the right and left rear audio signals, thus resulting in a large-scaled sound reproducing system.
As an alternative to the above, it may be thought of by those skilled in the art to adapt an AV (audio and video) amplifier employed in the Dolby surround system, wherein three front audio channels of L, R and C and one rear audio channel reproduced are for making four audio channels in total. However, as shown in FIG. 2, the AV amplifier for use in the Dolby surround system converts two-channel stereophonic sound signals of SL and SR, which are fed to input terminals of 1a and 1b, into four-channel, five signals by means of a contained surround processor 2, wherein the five signals are Right and Left front signals of FR and FL, Right and Left rear signals of RR and RL, whereas RR and RL are the same signal, and a Center front signal of FC.
In the circuit configuration as described above, the signals FL and FR are fed directly to main volume controllers 3a and 3b, while the signals RL, RR and FC are fed to main volume controllers 3c, 3d and 3e through balancing volume controllers 4a, 4b and 4c, whereby the sound volume as well as the acoustic balance of reproduced sounds are controlled respectively. The main volume controllers 3a-3e are interlocked each other in the operation.
Each audio signal controlled by the main volume controllers 3a-3e is output to each exterior speaker (not shown) from respective output terminals 7a-7e through connecting terminals 5a-5e and power amplifiers 6a-6e. This circuit configuration, however may cause a problem for the AV amplifier, in case of amplifying the audio signals in accordance with the Hi-vision 3-1 sound system, such that it is possible to apply the front audio signals of two channels R and L, but unable to apply the rear audio signal of one channel S and that the front center audio signal of one channel C thereunto.
To eliminate the above problem, connecting pins are pulled off from the connecting terminals, and the rear audio signal and the front center audio signal may be fed directly to the power amplifiers 6c-6e through the connecting terminals 5c-5e by applying the rear audio signal simultaneously on the audio channels R and L provided for amplifying the audio signals RR and RL and providing the front center audio signal on the audio channel C provided for amplifying the audio signal FC.
However, even with the modification, since the rear audio signal and the front center audio signal are fed directly to the power amplifiers 6c-6e as the audio signals of RR, RL and FC without passing through the volume controllers, another problem is caused such that there is no way to control the acoustic balance between the audio signals.